The present invention relates to a process for producing a presensitized lithographic printing plate. More particularly, the present invention relates to a process for producing a presensitized printing plate by coating a negative-working, light-sensitive composition with the aid of a particular solvent.
There are many known methods for producing presensitized lithographic printing plates by coating an aluminum plate with a light-sensitive composition containing a light-sensitive diazo resin and a high-molecular weight compound. See, for example, Japanese Patent Publication No. 1167/72 and Japanese Patent Application (OPI) Nos. 9804/73, 24404/72, 38302/72, 30604/75, 118802/75, and 120903/78 (the term "OPI" as used herein means an unexamined published patent application).
However, the conventional presensitized lithographic printing plates prepared by coating a solution of a light-sensitive composition onto a support having a hydrophilic surface, particularly an aluminum plate having a surface which has been rendered hydrophilic, have the disadvantage that their developability decreases with time and that the plates become soiled in non-image areas during printing.
Attempts have been made to eliminate this disadvantage by incorporating a variety of stabilizers in the light-sensitive layer. Among the stabilizers so far proposed for this purpose are the phosphorous acid described in Japanese Patent Application (OPI) No. 151023/79; the oxalic acid described in Japanese Patent Application (OPI) No. 3216/78; the halogen-containing organic phosphate ester compound described in Japanese Patent Application (OPI) No. 36207/75; the heterocyclic diazonium salt described in Japanese Patent Application (OPI) No. 143405/76; and the phosphoric acid, sulfuric acid, organic sulfonic acid, polyacrylic acid, polyvinylphosphonic acid, and polyvinylsulfonic acid as described in U.S. Pat. No. 3,679,419. These compounds have been found effective in improving the time-dependent developability of presensitized lithographic printing plates, but the results have not been completely satisfactory.